Working to Understand and Remedy Dead Zone in Green Bay, Wisconsin

Since 2010, NCCOS-sponsored scientists have studied Green Bay, Wisconsin to better understand the source, dynamics, and controls of low oxygen (hypoxia) conditions that have resulted in a “dead zone” in the southern end of the bay. Considered key to understanding hypoxia in Green Bay, researchers have focused on the land surrounding the bay, which accounts for one-third of the watershed’s runoff. This nutrient-rich runoff—loaded with phosphorus from farm fields, residential lawns, and city streets—fuels algal blooms in the bay that with increasing frequency have led to hypoxia as microbial decomposition of the blooms depletes the water of oxygen. Despite years of success steadily reducing the amount of phosphorus pollution from industrial processes and sewage discharges, the decades-old dead zone problem in the bay has worsened.

Dr. Val Klump of the University of Wisconsin–Milwaukee, NCCOS’s Green Bay project leader, oversees the computer modeling needed to predict how the complicated Green Bay ecosystem might respond to human attempts to reduce hypoxia. Project modeling shows Green Bay effectively traps nutrients and keeps them out of Lake Michigan; however, the amount trapped is bad for the bay. Modeling results thus far show that a 50 percent reduction in nutrient runoff might be sufficient to begin reversing hypoxic conditions in the bay.